This invention relates to the cooling of components such as printed circuit boards (PCB's) which have been subjected to a soldering operation in an automatic soldering machine.
Some PCB's do not have throughholes and these are known as surface mount devices (SMD's). A preferred soldering technique for SMD's is infrared (lR) reflow in which solder paste on the PCB's is caused to reflow upon the application of heat. More particularly, heating takes place in separately controlled zones within the machine permitting precise temperature profiling. The boards pass by wire mesh conveyor first into a preheat zone which gently heats the solder paste to drive off volatile solvents and avoid thermal shock to the PCB's. After preheating, the PCB's pass into the main heating zones where they are raised to reflow temperature. On exiting from the heating zones the boards are cooled, typically by blowing air up through the conveyor mesh, to solidify the solder joints.
A disadvantage With this conventional cooling system is that the bottom cooling fans bring turbulence into the heating zones when the PCB's are over the fans. This turbulent cool air entering the heating zones distrubs the process chamber environment. Another disadvantage is that the cooling across the conveyor is non-uniform so that the cooling across the PCB's is non-uniform. Furthermore solder and flux fumes Which leak out of the last heating zone and which are also generated during cooling are not dealt with by the conventional cooling system and these cause environmental pollution and discomfort to the operator.